JP3064774B2 - Continuous casting control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting control method for stabilizing continuous casting by automatically changing the casting speed based on the total torque of a driving roll.

[0002]

2. Description of the Related Art In a continuous casting method, a molten metal (hereinafter, referred to as molten steel) is poured into a tundish from a ladle, molten steel in a tundish is poured into a mold, and the molten steel is cooled by an inner surface of the mold to form a solidified portion. (Hereinafter referred to as a shell), and this shell is sandwiched and pulled out by a plurality of drive rolls.

Conventionally, a method of detecting a level of a molten steel surface in a mold and changing a casting speed (Japanese Patent Laid-Open No. 55-1497)
No. 61) and a method of changing the casting speed according to the mold size of the mold, the molten steel temperature, etc.
There is known a technique for stabilizing continuous casting by these methods.

It is known that the torque of a drive roll for pulling out a slab generally increases as the pulling speed increases, and decreases as the pulling speed decreases. Since the shell sandwiched between the drive roll and the driven roll has molten steel inside, for example, when the drawing speed is rapidly reduced, the shell between the rolls, such as the drive roll and the driven roll, is internally formed in a thin portion of the shell. The phenomenon of so-called bulging that occurs due to the pressure of molten steel occurs. When trying to pull out the shell in which bulging has occurred, a large load is temporarily applied to the drive roll, and the value of the torque of the drive roll increases. When the bulging is large, the load on the driving roll becomes excessive, and the shell may not be pulled out.

Therefore, conventionally, the operator manually changes the casting speed in consideration of the display of the torque value and other casting conditions so that the torque of the driving roll does not become too large, and for example, pulls out the slab. If the sum of the rotational torques of all the driving rolls (hereinafter, referred to as the sum of the torques) is too large, the casting speed is reduced to make the shell thicker so that large bulging does not occur.

[0006]

In the conventional casting monitoring method described above, since the torque value of the driving roll is not automatically controlled, the operator operates without noticing the abnormality. In the meantime, for example, a breakout prediction alarm is issued because the copper plate on the inner wall of the mold has become too hot, etc.When suddenly decelerating or suddenly stopping drawing, extremely thin parts of the shell Large bulging may occur, as shown in FIG.
If an attempt is made to increase the drawing speed after a sudden stop, the torque of the drive roll increases significantly, making drawing impossible, and a major problem has occurred in that the slab is solidified in the continuous casting machine.

[0007] As a method for preventing the torque value of the drive roll from being too large when the slab is drawn in continuous casting, the slab between the rolls is strongly cooled by secondary cooling water to prevent bulging. Can be considered. However, this method has a drawback that slab surface cracks are liable to occur, particularly in a steel type having a high susceptibility to crack on the slab surface, and that the slab temperature is too low.

The present invention has been made in view of the above circumstances, and an object of the present invention is to continuously cast without causing bulging, and in particular, even when the casting speed is suddenly reduced, the casting speed is not rapidly reduced. It is an object of the present invention to provide a continuous casting control method capable of returning to the same level as the above.

[0009]

Means for Solving the Problems To achieve the above object, a first aspect of the present invention is a casting method in continuous casting in which molten metal is poured into a mold and a slab is drawn out from below the mold by a plurality of driving rolls. Upon automatically controlling the speed, the sum of the rotational torques of all the drive rolls that are drawing the slab at the casting speed is detected, and the rotational torque set in accordance with the detected value of the total of the rotational torques and the slab width in advance. A continuous casting control method, wherein the casting speed is reduced within a range of not more than a preset deceleration value when the detected value exceeds the upper limit value. Is what you do.

[0010] In a second aspect of the present invention, there is provided the continuous casting method, wherein the detected value is smaller than the upper limit value and the casting speed is lower than a predetermined casting speed. The present invention provides a continuous casting control method characterized in that the casting speed is accelerated within a range of a preset acceleration value or less.

[0011]

According to the continuous casting control method of the first aspect of the present invention, the total of the rotational torques of all the drive rolls is detected, and the detected value is set to the upper limit of the total of the rotational torques set in advance according to the slab width. When the detected value of the total torque is larger than the upper limit, the casting speed is reduced in a range not more than a preset value, and the casting speed is reduced so that the shell is not thickened and large bulging occurs. Is automatically controlled, the slab cannot be pulled out during continuous casting (casting), the slab does not solidify, and a stable operation can be performed. Further, the continuous casting control method according to the second aspect of the present invention, in addition to the first aspect, further includes a detection value of the total torque is smaller than an upper limit value, and a casting speed is set in advance by casting conditions such as a slab width. If the casting speed is lower than the predetermined casting speed, the casting speed is automatically controlled so as to accelerate in a range equal to or less than a preset value. be able to.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A continuous casting control method according to the present invention will be described in detail below based on a preferred embodiment shown in the accompanying drawings. Prior to the description of the continuous casting control method of the present invention, a continuous casting facility suitably used in the continuous casting control method of the present invention will be described.

FIG. 3 is a cross-sectional view showing a part of an embodiment of a continuous casting facility for implementing the continuous casting control method of the present invention. In this figure, reference numeral 10 denotes a continuous casting facility.
Reference numeral 12 denotes a tundish.

The tundish 12 is for injecting molten steel 11 from a ladle (not shown) to float and separate nonmetallic inclusions, and a lower nozzle 13 such as a sliding nozzle is attached to the lower end thereof. In the lower nozzle 13,
An adjusting mechanism for adjusting the flow rate of the molten steel 11 is provided,
One end of the immersion nozzle 14 is joined to the lower end.

The immersion nozzle 14 is a tubular body made of a refractory, and its tip is immersed in the molten steel 11 in the mold 16.

The mold 16 is for continuously forming a slab 30 having a rectangular cross section and a predetermined dimension, and is constituted by opposing long sides 16a and opposing short sides (not shown).
The molten steel 11 discharged from the immersion nozzle 14 is cooled to form a shell 31.

Below the mold 16, a driven roll 17 for holding a shell 31 containing the molten steel 11 and a shell 3
A large number of drive rolls 18 are provided to hold the roller 1 and pull it out of the mold 16.
Are driven to rotate by a plurality of drive motors 20. A drive device 45 is connected to these drive motors 20 as shown in FIG. This driving device 45
Supplies a current corresponding to the rotation speed in order to rotate the drive motor 20 at a predetermined rotation speed.

FIG. 1 is a block diagram showing an embodiment of a control system 40 of the continuous casting control method according to the present invention. The control system 40 controls the sum of torques (of all the drive rolls 18 pulling out the slab). An adder 43 for inputting a detection value 41 of the sum of rotational torques) and an upper limit value 42 of the total torque set in advance according to casting conditions such as a slab width, according to the size of the added data sent from the adder 43 In order to control the casting speed, that is, the rotation speed of the drive roll 18, a determination unit 44 that sets a current value to be supplied to the motor 20 that determines the rotation speed of the motor 20, The driving current corresponding to this is
And a driving device 45 for supplying the power to the motor.

An upper limit of the total torque for each slab width is set in the control system 40 in advance, and the control system 40 receives the upper limit of the total torque by inputting the slab width at the start of casting. Set the value.
In general, a slab having a wider width requires a larger torque for drawing, and for a slab having a thickness of 260 mm, the present inventors have experience and the like, and the upper limit shown in Table 1 is appropriate. I got that.

Next, the continuous casting control method of the present invention will be described. FIG. 2 is a flowchart showing one embodiment of the continuous casting control method of the present invention. First, at the start of casting, the drive unit 45 is operated to supply current to the motor 20, and casting conditions such as steel type and slab width are input.
Then, the target casting speed (predetermined casting speed) is set,
Set the target current value. The target casting speed and the target current value are output to the driving device. Then, the upper limit of the total torque is set according to the casting conditions such as the slab width.

Then, for example, at every detection timing of every five minutes, the casting speed and the current value continuously sent from the driving device are picked up. Then, the total torque is detected, and the detected value is compared with a preset upper limit value,
If the detected value exceeds the upper limit, a deceleration current value corresponding to a preset deceleration value (for example, -0.3 m / min) is output to the driving device. When the detected value does not exceed the upper limit value, the casting speed is compared with a preset target casting speed, and when the detected value is lower than the target casting speed, the casting speed is adjusted according to a speed increase value (for example, +0.3 m / min). The increased speed current value is output to the driving device. Also, the detected value does not exceed the upper limit,
When the casting speed is the target casting speed, the target casting speed is maintained. Then, when a predetermined detection timing is reached, similar processing and determination are performed from the pickup of the casting speed and the current value. Then, when it is time to end the casting, the control system stops. That is, the control system detects the sum of the torques of the drive rolls at predetermined time intervals, and automatically controls the sum of the torques to be equal to or less than the upper limit value and the casting speed to be equal to or close to the target casting speed. Is controlled.

Here, the detection of the total torque may be calculated from the current value supplied to all the motors 20 for driving all the driving rolls 18 and the load applied to all the motors 20. It may be calculated from the rotation speed and the load of the driving roll 18 or all the motors 20,
A torque meter may be attached to all of the drive rolls 18 or all of the motors 20 to directly detect them individually, and all of them may be added to obtain a total sum.

According to the continuous casting control method described above, continuous casting can be performed without generating a large torque on the drive roll, and in particular, even when the casting speed is suddenly reduced, the drawing becomes impossible. Such a trouble does not occur, and the casting speed can be returned to the same level as before the sudden deceleration.

It should be noted that the present invention is not limited to the above embodiment, but includes a detection time interval, a preset deceleration value and an increase value of the casting speed, a casting speed, a current value,
The control system programs, such as various timings such as torque pickup (detection), calculation, and calculation timing, can be appropriately changed according to the steel type, slab thickness, structure of the continuous casting facility, and the like. In addition, the control method of the present invention can be used in combination with other commonly used control methods. For example, the lower part of the tundish 12 can be used in response to the reduction and acceleration of the casting speed. The nozzle 13 may be automatically adjusted to keep the level of the molten metal in the mold 16 constant, and the amount of cooling water may be automatically adjusted so as not to cause overcooling.

(Embodiment) The continuous casting control method of the present invention
A slab was formed using a continuous casting facility 10 as shown in FIG. 3 and applied to continuous casting of ordinary steel. The casting conditions were: target casting speed: 1.7 m / min and 1.5 m / m
In slab width: 1700 mm, and the upper limit of the total torque is 150 ton · m as shown in Table 1. Then, set the deceleration value to -0.3
m / min, the set acceleration value is +0.3 m / min, and the drive roll torque detection timing (time interval) is 5 m.
in every other.

FIGS. 4, 5 and 6 are graphs showing the change over time in the sum of the casting speed and the torque in the embodiment of the continuous casting control method of the present invention. FIG. 7 is a graph showing the change over time of the sum of the conventional casting speed and torque. The target casting speed of the embodiment of the present invention shown in FIGS. 4 and 5 is 1.7.
m / min, and the target casting speed of the inventive example of FIG. 6 and the comparative example of FIG. 7 is 1.5 m / min.

In the change with time shown in FIG. 4, the sum of the torque detected at the detection timing exceeds the upper limit of 150 ton · m, and the casting speed at this time was 1.7 m / min. Then, the deceleration current value was automatically output to the drive device, the current value supplied to the motor was reduced, the rotation speed of the motor was reduced, and the casting speed was 1.4 m / min. Then, at the next detection timing, since the total torque was less than 150 ton · m, the casting speed was automatically accelerated to the target of 1.7 m / min.

The time-dependent change shown in FIG. 5 indicates that the total torque detected at the detection timing is equal to the upper limit of 150 ton · m.
And the casting speed at this time was 1.7 m / min. Therefore, the deceleration current value is automatically output to the driving device, the current value supplied to the motor is reduced, the rotation speed of the motor is reduced, the casting speed becomes 1.4 m / min, and at the next detection timing, Also, the sum of the torque is 1
It exceeded 50 ton · m, and the speed was automatically reduced again to 1.1 m / min.

The time-dependent change shown in FIG. 6 indicates that the total torque detected at the detection timing is equal to the upper limit of 150 ton · m.
And the casting speed at this time was 1.5 m / min. Therefore, the casting speed is 1.2 m /
min. Thereafter, the sum of the casting speed and the torque sharply decreased due to the occurrence of the breakout alarm. Thereafter, as the casting speed increased, the total torque suddenly increased, but the total torque gradually increased and returned to the target casting speed of 1.5 m / min.

The time-dependent change shown in FIG. 7 indicates that continuous casting is performed at the target casting speed of 1.5 m / min, and a breakout alarm is issued when the total torque exceeds the upper limit of 150 ton · m. Immediately thereafter, the sum of the casting speed and the torque sharply decreased. Thereafter, an attempt was made to increase the casting speed, but the torque of the drive roll increased remarkably, making it impossible to pull out the material.

By suppressing the increase in the torque value and preventing the occurrence of large bulging as described above, continuous casting can be stably performed. In particular, it is possible to continue drawing even after the casting speed is rapidly reduced. As a result, the casting speed could be returned to the same level as before the rapid deceleration.

[0032]

According to the continuous casting method of the first aspect of the present invention, the casting speed is automatically controlled so that bulging does not occur, so that the drawing is continued even when the casting speed is suddenly reduced. The slab does not solidify in the mold, and a stable operation can be performed. In addition, since the casting speed is automatically controlled, the operator does not need to monitor the torque value and change the speed due to an abnormal torque value, which reduces the operator's work. Reduction is possible.

According to the continuous casting control method of the second aspect of the present invention, in addition to the first aspect, the detected value of the total torque is smaller than the upper limit value and the casting speed is determined in advance by the slab width or the like. If the casting speed is smaller than a predetermined casting speed set by the casting conditions, the casting speed is automatically controlled so as to accelerate in a range equal to or less than a preset value. Operation can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a control system for implementing a continuous casting control method of the present invention.

FIG. 2 is a flowchart showing one embodiment of the continuous casting control method of the present invention.

FIG. 3 is a cross-sectional view of a part of a continuous casting facility used in the continuous casting control method of the present invention.

FIG. 4 is a graph showing the sum of the casting speed and the torque of the first embodiment of the continuous casting to which the continuous casting control method of the present invention is applied.

FIG. 5 is a graph showing the sum of the casting speed and the torque in the second embodiment of the continuous casting to which the continuous casting control method of the present invention is applied.

FIG. 6 is a graph showing the sum of the casting speed and the torque of the third embodiment of the continuous casting to which the continuous casting control method of the present invention is applied.

FIG. 7 is a graph showing the sum of the casting speed and the torque when the casting speed is rapidly reduced.

DESCRIPTION OF SYMBOLS 10 Continuous casting equipment 11 Molten steel 12 Tundish 13 Lower nozzle 14 Immersion nozzle 16 Mold 17 Follower roll 18 Drive roll 20 Motor 30 Slab 40 Control system 41 Detection value 42 Upper limit value 43 Adder 44 Judge 45 Drive

Continuation of the front page (56) References JP-A-63-171258 (JP, A) JP-A-60-227958 (JP, A) JP-A-60-191649 (JP, A) JP-A-57-75260 (JP) JP-A-53-132430 (JP, A) JP-A-7-24560 (JP, A) JP-A-6-154983 (JP, A) JP-A-4-100666 (JP, A) 3-254344 (JP, A) JP-A-63-215359 (JP, A) JP-A-6-106317 (JP, A) JP-A-5-169215 (JP, A) JP-A-59-225866 (JP, A) A) JP-A-56-158266 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/20 B22D 11/16 104

Claims (2)

(57) [Claims] 1. A method for automatically controlling a casting speed in continuous casting in which molten metal is poured into a mold and a plurality of drive rolls are used to draw the slab from below the mold, wherein all of the slabs that are being drawn at the casting speed are used. The total sum of the rotational torques of the drive rolls is detected, and the detected value of the total of the rotational torques is compared with an upper limit of the total of the rotational torques set in advance according to the slab width, and the detected value exceeds the upper limit. Wherein the casting speed is automatically reduced within a range equal to or less than a preset deceleration value. 2. The continuous casting control method according to claim 1, further comprising: when the detected value is smaller than the upper limit value and the casting speed is lower than a predetermined casting speed. A continuous casting control method, wherein the casting speed is automatically accelerated within a range of a preset acceleration value or less.